During the manufacture of integrated circuits, commonly referred to as semiconductor chips or microchips, several iterations of a photolithographic process are used. In this manufacturing process, dielectric, barrier or electrically conducting layers of silicon dioxide, silicon nitride, or metal are deposited upon a substrate such as a silicon or gallium arsenide wafer by thermal oxidation, chemical vapor deposition, sputtering, ion implantation, vacuum evaporation, or similar means. After these layers are deposited, a photoresist material is coated onto the surface of the wafer by, for example, spinning the wafer to distribute liquid photoresist material evenly on the surface of the wafer. Usually the coated wafer is heated in a “soft bake” or prebake step to improve adhesion of the photoresist material to the surface and to remove solvent from the photoresist material.
After the photoresist material is “soft baked”, selected portions of the wafer are exposed to high energy light, such as high intensity ultraviolet light, in a desired pattern defined by a photomask. Developing agents are then used to develop the portions of the photoresist material that were exposed to the high-energy light. When the photoresist material is a positive photoresist material, the developed portions are solubilized by the light exposure and then washed away. This leaves some portions of the wafer exposed and other portions coated with dielectric or conducting layer underneath the remaining, unexposed and undeveloped photoresist layer. Conversely, when the photoresist material is a negative photoresist material, the undeveloped portions are selectively removed.
Once the pattern of photoresist material has been established on the wafer, the wafer is “hard baked” to densify and toughen the photoresist material and to further improve adhesion. The exposed substrate and/or barrier material is then etched (removed) by any of several suitable methods, depending upon the materials used to prepare the dielectric or conducting layer; wet chemical etching, dry etching, plasma etching, sputter etching or reactive-ion etching processes, for example, may be used. The etching processes remove barrier material that is unprotected by photoresist material, leaving both portions of bare wafer and portions of wafer having layered coatings of barrier layer and photoresist material that protected the barrier layer underneath from being etched away. The wafer is then treated in an aggressive step to remove the hard baked photoresist material. This has traditionally been done using solvent washes of halogenated hydrocarbons, mixtures of sulfuric acid and hydrogen peroxide, or highly alkaline mixtures of hydroxides and activators. Use of any of these solvent mixtures produces large volumes of undesirable wastes. After the hard-baked photoresist material is removed, the wafer is washed with deionized water to remove all traces of photoresist removal solvents, and treated with isopropyl alcohol to remove any residual water.
This photolithographic process is repeated as many times as needed to produce as many layers of different patterns of dielectric, barrier or conducting layer material upon the substrate as desired. Layers of either positive or negative photoresist material can be used in various combinations on the same wafer.
The solvent washing step, wherein the wafer is washed with halogenated hydrocarbons, mixtures of sulfuric acid and hydrogen peroxide, or highly alkaline mixtures of hydroxides and activators, generates large volumes of waste that must be disposed of at great cost. There is a need for a method and composition for removing photoresist materials from electronic components that reduces the amount of undesirable wastes.
Therefore it is an object of this invention to provide a method of removing photoresist materials during the manufacture of electronic components such as integrated circuits, circuit boards, optical waveguides and flat panel displays.
Another object of the invention is to provide a composition for removing photoresist materials from electronic components.
Another object of the invention is to provide a method for reducing the amount of waste generated during removal of photoresist materials from electronic components.
Another object of the invention is to provide a method for removing photoresist materials from integrated circuit features less than 0.1 microns in size.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. The claims appended hereto are intended to cover all changes and modifications within the spirit and scope thereof.